There are many arrangements wherein conveyors buffer flow of articles through a system. One common use is in systems for filling liquid containers such as bottles, cans or boxes. In such systems, to achieve first-in/first-out flow, an accumulator with oppositely-running conveyors can be located between an upstream station (e.g., a filler) and a downstream station (e.g. a capper). The conveyors may be straight and horizontal, and may be in the form of “mass-flow, linear” conveyors. Alternatively, the conveyors may be curved and non-horizontal, and may be in the form of “single-file, helical” conveyors. One of the conveyors (e.g., an infeed conveyor) receives articles from the system and the other conveyor (e.g., an outfeed conveyor) returns articles to the system. A transfer device moves articles from the infeed conveyor to the outfeed conveyor. Articles thus flow from the system, through the infeed conveyor, transfer device, and outfeed conveyor, and then back to the system.
When the upstream and downstream stations run at the same speed (in terms of articles per minute, for example), the accumulator generally operates in a steady state. When the infeed and outfeed conveyors are moved at the same speed and the transfer device is stationary. If the downstream station slows or stops, the device leaves steady state. The outfeed conveyor slows or stops accordingly, while the infeed conveyor continues and the transfer device moves so that more articles enter the accumulator. As long as the downstream station returns to service before the accumulator is filled, then the overall system need not be stopped or slowed. Similarly, if the upstream device slows or stops, the infeed conveyor slows or stops accordingly, and the outfeed conveyor continues at full speed as long as a supply of articles is available in the accumulator. As long as the upstream device returns to service before the accumulator is emptied, then the overall system need not be stopped or slowed.
Many of such accumulator devices have been successfully deployed. In particular, Applicant has commercially introduced, and is owner of U.S. patents on, various types of mass-flow and single file accumulators under the DYNAC® name. For example, U.S. Pat. Nos. 6,382,398 and 6,497,321 disclose respectively horizontal, mass-flow and helical, single-file accumulators. U.S. Pat. No. 6,698,581 also discloses a helical, single file accumulator, as well as aspects of designs for a device for transferring articles from an infeed conveyor to an outfeed conveyor. The transfer device is driven along the infeed and outfeed conveyors when the conveyors are running at different speeds to accumulate or de-accumulate articles on the conveyors as dictated by the system in which the accumulator is placed.
The devices and systems introduced by Applicant and disclosed in the above patents provide exemplary operation in their intended systems. However, further improvement would be welcome, in particular in providing designs for higher speed accumulators, transfer devices and systems, in which operational throughput of articles is increased, or in providing designs capable of handling articles of different dimensions, with less adjustment or changeout of parts.